i cann't install isa 2006??

You cannot do this - ISA is 32-bit only, runs on Windows 2003 - 32-bit and cannot be installed on Windows server 2008 which is 64-bit.

if you can install hyper-v and use a Windows 2003 32-bit hyper-v guest then that is your only option or install a windows server 32-bit server.

ISA 2006 cannot be installed on windows 2008 even 32 bits version of it.

I think Keith was talking about 2008 R2 which is only 64bits but ISA 2006 can only be installed on windows 2003 32 bits.

you will need the new ISA called TMG that can only run on 64 bits machines

http://www.microsoft.com/forefront/edgesecurity/isaserver/en/us/default.aspx

http://www.microsoft.com/presspass/press/2008/apr08/04-08ForefrontBetaPR.mspx

Akhater - please do not 'assume' to make comments about another experts comments unless you are certain of your facts.

well sorry i offended it was just more polite than writing you are saying something wrong.

2008 has a 32 bits version 2008 R2 doesn't and i'm sure you know that you simply wrote something different

Not a problem - be assured though I will watch your comments in the future with vigour to ensure I can reciprocate and return the favour each time the opportunity presents itself

thank you keith for reply but i install windows 2008 32 bit so can you advice me how can i do ??

you cannot. As I mentioned in my first post - ISA 2008 is not a supportable operating system for ISA Server. ISA requires windows 2003 - 32 bit.

Therefore it is impossible to install ISA on Windows Server 2008 , I suggest to create  Virtual Machine after installing Hyper-V(you can find it as Role like DHCP and DNS ) , and then install Windows Server 2003 and then ISA.

That is the only way to do it , all sustem administrators are using Virtualization nowadays , it is hot topic in fact.

it's works on windows 2008 64bit